It doesn't return a correct result...

Hi,

I'm doing the first exercise on struct. I can't figure out why it doesn't return a correct result for median. It always rounds it up... Say if I input 1 2 3 4, it returns the median == 3, not 2.5, even though it uses type double. Could you please help? Also, could you please help suggest a bit of improvement on the program? I'm learning about struct/class and this exercises asks me to practice using struct...

Code:

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// Exercise 8.12
#include "std_lib_facilities.h"
/*
        Write a function that finds the smallest & the largest element of vector
        argument and also compute the mean and the median. Do not use global variables.
        Either return a struct containing results or pass them back through reference
        arguments. Which one do you prefer, and why?

*/

struct stats {
        vector<double> v;
        double smallest, largest, median;
        double fmean(vector<double>& v);
        double fmedian(vector<double>& v);
        double fsmallest(vector<double>& v);
        double flargest(vector<double>& v);
};

int main()
try {
        stats mystats;
        vector<double> v;
        double x;
        cout << "Enter some elements for a vector: \n";
        while (cin >> x)
                v.push_back(x);
        cout << "Here are some summary statistics: \n";
        cout << "Smallest: " << mystats.fsmallest(v) << '\n';
        cout << "Largest: " << mystats.flargest(v) << '\n';
        cout << "Mean: " << mystats.fmean(v) << '\n';
        cout << "Median: " << mystats.fmedian(v) << '\n';
       
}
catch (runtime_error e) {
        cout << e.what();
}

double stats::fsmallest(vector<double>& v)
{
        smallest = v[0];
        for (unsigned int i = 0; i < v.size(); ++i) {
                if (v[i] < smallest)
                        smallest = v[i];
        }
        return smallest;
}

double stats::flargest(vector<double>& v)
{
        largest = v[0];
        for (unsigned int i = 0; i < v.size(); ++i) {
                if (v[i] > largest)
                        largest = v[i];
        }
        return largest;
}

double stats::fmean(vector<double>& v)
{
        double sum = 0;
        for (unsigned int i = 0; i < v.size(); ++i) {
                sum += v[i];
        }
        return sum / v.size();
}

double stats:: fmedian(vector<double>& v)
{
        sort(v.begin(), v.end());
        median = 0;
        for (unsigned int i = 0; i < v.size(); ++i) {
                if (v.size()%2==0)
                        median = (v[v.size()/2] + v[v.size()/2-1])/2;
                median = v[v.size()/2];       
        }
        return median;
}

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Quote:

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Code:

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if (v.size()%2==0)
  median = (v[v.size()/2] + v[v.size()/2-1])/2;
median = v[v.size()/2];

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Perhaps you intended to place an else in there somewhere?

Quote:

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Originally Posted by ctrl_freak

Perhaps you intended to place an else in there somewhere?

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Thanks a lot, ctrl_freak. I should have put else just before median... Thanks for helping

I want to ask what "std_lib_facilities.h" is ? I can't find it in head files. I use the ubuntu OS.

Quote:

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Originally Posted by okgays

I want to ask what "std_lib_facilities.h" is ? I can't find it in head files. I use the ubuntu OS.

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It's a header file used in the new book by Bjarne Stroustrup. I'm learning C++ from this book, so I copy it & use it in every program.

>I want to ask what "std_lib_facilities.h" is ?
http://www.stroustrup.com/Programmin...b_facilities.h